Abstract:

A process for the ammoxidation of a saturated or unsaturated or mixture of
saturated and unsaturated hydrocarbon to produce an unsaturated nitrile,
said process comprising contacting the saturated or unsaturated or
mixture of saturated and unsaturated hydrocarbon with ammonia and an
oxygen-containing gas in the presence of a catalyst composition
comprising molybdenum, vanadium, antimony, niobium, tellurium, optionally
at least one element select from the group consisting of titanium, tin,
germanium, zirconium, hafnium, and optionally at least one lanthanide
selected from the group consisting of lanthanum, cerium, praseodymium,
neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium,
thulium, ytterbium and lutetium. Such catalysts are characterized by very
low levels of tellurium in the composition. Such catalyst compositions
are effective for the gas-phase conversion of propane to acrylonitrile
and isobutane to methacrylonitrile (via ammoxidation).

Claims:

1. A process for the ammoxidation of a saturated or unsaturated or mixture
of saturated and unsaturated hydrocarbon to produce an unsaturated
nitrile, said process comprising contacting the saturated or unsaturated
or mixture of saturated and unsaturated hydrocarbon with ammonia and an
oxygen-containing gas in the presence of a catalyst composition
comprising a mixed oxide of empirical
formula:Mo1VaSb.sub.bNbcTedXeLfOn
wherein X is selected from the group consisting of Ti, Sn, Ge, Zr, Hf,
and mixtures thereof; L is selected from the group consisting of La, Ce,
Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and mixtures
thereof;0.1<a<0.8,0.01<b<0.6,0.001<c<0.3,0.001<d<-
0.06,0.ltoreq.e<0.6,0.ltoreq.f<0.1; andn is the number of oxygen
atoms required to satisfy valance requirements of all other elements
present in the mixed oxide with the proviso that one or more of the other
elements in the mixed oxide can be present in an oxidation state lower
than its highest oxidation state, and wherein a, b, c, d, e and f
represent the molar ratio of the corresponding element to one mole of Mo.

3. The process of claim 1, wherein X is selected from the group consisting
of elements Ti, Sn and mixtures thereof.

4. The process of claim 1, wherein L is selected from the group consisting
of elements Nd, Ce, Pr and mixtures thereof.

5. The process of claim 1, wherein the catalyst composition comprises a
support selected from the group consisting of silica, alumina, zirconia,
titania, or mixtures thereof.

6. The process of claim 5, wherein the support comprises about 10 to about
70 weight percent of the catalyst.

7. The process of claim 1, wherein the hydrocarbon includes propane,
isobutane, or a mixture thereof.

8. The process of claim 1, wherein the process includes providing a feed
stream comprising saturated or unsaturated or mixture of saturated and
unsaturated hydrocarbon, ammonia, and an oxygen-containing gas, wherein
the molar ratio of hydrocarbon to oxygen is from about 0.125 to about 5.

9. The process of claim 1, wherein the process includes providing a feed
stream comprising saturated or unsaturated or mixture of saturated and
unsaturated hydrocarbon, ammonia, and an oxygen-containing gas, wherein
the molar ratio of hydrocarbon to ammonia is from about 0.3 to about 2.5.

10. The process of claim 1, wherein the process includes providing a feed
stream comprising saturated or unsaturated or mixture of saturated and
unsaturated hydrocarbon at a flow rate that is controlled to provide a
weight hourly space velocity of at least about 0.1 grams hydrocarbon to
grams of catalyst.

11. The process of claim 1, wherein the process includes providing a feed
stream comprising saturated or unsaturated or mixture of saturated and
unsaturated hydrocarbon at a flow rate that is controlled to provide a
weight hourly space velocity of at least about 0.15 grams hydrocarbon to
grams of catalyst.

12. The process of claim 1, wherein the process includes providing a feed
stream comprising saturated or unsaturated or mixture of saturated and
unsaturated hydrocarbon at a flow rate that is controlled to provide a
weight hourly space velocity of at least about 0.2 grams hydrocarbon to
grams of catalyst.

13. A process for the ammoxidation of a saturated or unsaturated or
mixture of saturated and unsaturated hydrocarbon to produce an
unsaturated nitrile, said process comprising contacting the saturated or
unsaturated or mixture of saturated and unsaturated hydrocarbon with
ammonia and an oxygen-containing gas in the presence of a catalyst
composition comprising a mixed oxide of empirical
formula:Mo1VaSb.sub.bNbcTedXeLfAgLi.su-
b.hOn wherein X is selected from the group consisting of Ti, Sn, Ge,
Zr, Hf, and mixtures thereof; L is selected from the group consisting of
La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and mixtures
thereof; A is at least one of Na, K, Cs, Rb and mixtures
thereof;0.1<a<0.8,0.01<b<0.6,0.001<c<0.3,0.001<d<-
0.06,0.ltoreq.e<0.6,0.ltoreq.f<0.1,0.ltoreq.g<0.1,0.ltoreq.h<0-
.1, andn is the number of oxygen atoms required to satisfy valance
requirements of all other elements present in the mixed oxide with the
proviso that one or more of the other elements in the mixed oxide can be
present in an oxidation state lower than its highest oxidation state, and
wherein a, b, c, d, e, f, g, and h represent the molar ratio of the
corresponding element to one mole of Mo.

[0003]The present invention generally relates to a process for the
ammoxidation or oxidation of a saturated or unsaturated hydrocarbon to
produce an unsaturated nitrile or an unsaturated organic acid.

[0004]The invention particularly relates to a process for the gas-phase
conversion of propane to acrylonitrile and isobutane to methacrylonitrile
(via ammoxidation) or of propane to acrylic acid and isobutane to
methacrylic acid (via oxidation).

[0005]2. Description of the Prior Art

[0006]Mixed metal oxide catalysts have been employed for the conversion of
propane to acrylonitrile and isobutane to methacrylonitrile (via an
ammoxidation reaction) and/or for conversion of propane to acrylic acid
(via an oxidation reaction). The art known in this field includes
numerous patents and patent applications, including for example, U.S.
Pat. No. 5,750,760 to Ushikubo et al., U.S. Pat. No. 6,036,880 to Komada
et al., U.S. Pat. No. 6,043,186 to Komada et al., U.S. Pat. No. 6,143,916
to Hinago et al., U.S. Pat. No. 6,514,902 to Inoue et al., U.S. Patent
Application No. US 2003/0088118 A1 by Komada et al., U.S. Patent
Application No. 2004/0063990 A1 to Gaffney et al., and PCT Patent
Application No. WO 2004/108278 A1 by Asahi Kasei Kabushiki Kaisha

[0007]Although advancements have been made in the art in connection with
catalysts containing molybdenum, vanadium, antimony and niobium effective
for the conversion of propane to acrylonitrile and isobutane to
methacrylonitrile (via an ammoxidation reaction) and/or for the
conversion of propane to acrylic acid and isobutane to methacrylic acid
(via an oxidation reaction), the catalysts need further improvement
before becoming commercially viable. In general, the art-known catalytic
systems for such reactions suffer from generally low yields of the
desired product.

[0008]Tellurium can become volatile at the temperatures used for the
ammoxidation of propane and isobutane and/or for the conversion of
propane to acrylic acid and isobutane to methacrylic acid (via an
oxidation reaction). Catalysts containing relatively high amounts of
tellurium have exhibited a loss of tellurium during the ammoxidation or
oxidation operation. Catalyst performance can be negatively impacted by
the loss of tellurium.

SUMMARY OF THE INVENTION

[0009]In one aspect, the present invention relates to a process for the
ammoxidation of a saturated or unsaturated or mixture of saturated and
unsaturated hydrocarbon to produce an unsaturated nitrile, the process
comprising contacting the saturated or unsaturated or mixture of
saturated and unsaturated hydrocarbon with ammonia and an
oxygen-containing gas in the presence of a catalyst composition
comprising molybdenum, vanadium, antimony, niobium, tellurium, optionally
at least one element selected from the group consisting of titanium, tin,
germanium, zirconium, and hafnium, and optionally at least one lanthanide
selected from the group consisting of lanthanum, cerium, praseodymium,
neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium,
thulium, ytterbium, and lutetium. The catalyst composition used in this
process is further characterized by relatively low levels of tellurium in
the composition.

[0010]In one embodiment, the present invention is a process for the
conversion of a hydrocarbon selected from the group consisting of
propane, isobutane or mixtures thereof, to acrylonitrile,
methacrylonitrile, or mixtures thereof, the process comprising the step
of reacting in the vapor phase at an elevated temperature said
hydrocarbon with a molecular oxygen-containing gas and ammonia, in the
presence of a catalyst composition comprising molybdenum, vanadium,
antimony, niobium, tellurium, optionally at least one element selected
from the group consisting of titanium, tin, germanium, zirconium, and
hafnium, and optionally at least one lanthanide selected from the group
consisting of lanthanum, cerium, praseodymium, neodymium, samarium,
europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium,
and lutetium.

[0011]In another aspect, the present invention also relates to
ammoxidation catalyst compositions comprising molybdenum, vanadium,
antimony, niobium, tellurium, optionally at least one element selected
from the group consisting of titanium, tin, germanium, zirconium, and
hafnium, and optionally at least one lanthanide selected from the group
consisting of lanthanum, cerium, praseodymium, neodymium, samarium,
europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium,
and lutetium.

[0012]In one embodiment, the catalyst composition comprises a mixed oxide
of empirical formula:

Mo1VaSb.sub.bNbcTedXeLfOn[0013]wherein X is selected from the group consisting of Ti, Sn, Ge, Zr,
Hf, and mixtures thereof, [0014]L is selected from the group consisting
of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and mixtures
thereof, [0015]0.1<a<0.8, [0016]0.01<b<0.6,
[0017]0.001<c<0.3, [0018]0.001<d<0.06,
[0019]0≦e<0.6, [0020]0a≦f<0.1; and [0021]n is the
number of oxygen atoms required to satisfy valance requirements of all
other elements present in the mixed oxide with the proviso that one or
more of the other elements in the mixed oxide can be present in an
oxidation state lower than its highest oxidation state, and [0022]a, b,
c, d, e and f represent the molar ratio of the corresponding element to
one mole of Mo.

[0023]In other embodiments X is Ti, Sn or mixtures thereof.

[0024]In other embodiments, L is Nd, Ce, or Pr.

DETAILED DESCRIPTION OF THE INVENTION

[0025]The present invention generally relates to a process for the
(amm)oxidation of a saturated or unsaturated hydrocarbon, and catalyst
compositions that may be used in the process. Such processes are
effective for the ammoxidation of propane to acrylonitrile and isobutane
to methacrylonitrile and/or for the conversion of propane to acrylic acid
and isobutane to methacrylic acid (via an oxidation reaction).

Catalyst Composition

[0026]In one embodiment, the catalyst composition employed in the process
of the present invention comprises molybdenum, vanadium, antimony,
niobium, tellurium, optionally at least one element selected from the
group consisting of titanium, tin, germanium, zirconium, and hafnium, and
optionally at least one lanthanide selected from the group consisting of
lanthanum, cerium, praseodymium, neodymium, samarium, europium,
gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, and
lutetium. The catalyst composition used in this process is further
characterized by relatively low levels of tellurium in the composition,
such that in one embodiment, the molybdenum to tellurium molar ratio
(Mo:Te) is between 1:0.001 and 1:0.06. In another embodiment, the
molybdenum to tellurium molar ratio (Mo:Te) is between 1:0.001 and
1:0.05. As used herein, "at least one element selected from the group . .
. " or "at least one lanthanide selected from the group . . . " includes
within in its scope mixtures of two or more of the listed elements or
lanthanides, respectively.

[0027]In one embodiment, the catalyst composition comprises a mixed oxide
of empirical formula:

Mo1VaSb.sub.bNbcTedXeLfOn[0028]wherein X is selected from the group consisting of Ti, Sn, Ge, Zr,
Hf, and mixtures thereof; [0029]L is selected from the group consisting
of La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and mixtures
thereof; [0030]0.1<a<0.8, [0031]0.01<b<0.6,
[0032]0.001<c<0.3, [0033]0.001<d<0.06,
[0034]0≦e<0.6, [0035]0≦f<0.1; and [0036]n is the
number of oxygen atoms required to satisfy valance requirements of all
other elements present in the mixed oxide with the proviso that one or
more of the other elements in the mixed oxide can be present in an
oxidation state lower than its highest oxidation state, and, [0037]a, b,
c, d, e and f represent the molar ratio of the corresponding element to
one mole of Mo.

[0038]In one embodiment, the catalyst composition comprises a mixed oxide
of empirical formula:

Mo1VaSb.sub.bNbcTedXeLfOn[0039]wherein X is selected from the group consisting of Ti, Sn, and
mixtures thereof; [0040]L is selected from the group consisting of La,
Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and mixtures thereof;
[0041]0.1<a<0.8, [0042]0.01<b<0.6, [0043]0.001<c<0.3,
[0044]0.001<d<0.06, [0045]0≦e<0.6,
[0046]0≦f<0.1; and [0047]n is the number of oxygen atoms
required to satisfy valance requirements of all other elements present in
the mixed oxide with the proviso that one or more of the other elements
in the mixed oxide can be present in an oxidation state lower than its
highest oxidation state, and [0048]a, b, c, d, e and f represent the
molar ratio of the corresponding element to one mole of Mo.

[0049]In other embodiments of the catalyst compositions described by the
above empirical formulas, X is one of Ti or Sn. In other embodiments of
the catalyst compositions described by the above empirical formulas, X is
Ti, X is Sn, X is Ge, X is Zr, and X is Hf.

[0050]In other embodiments of the catalyst compositions described by the
above empirical formulas, L is one of Nd, Ce, or Pr. In another
embodiments, L is one of Nd or Pr. In other embodiments of the catalyst
compositions described by the above empirical formulas, L is La, L is Ce,
L is Pr, L is Nd, L is Sm, L is Eu, L is Gd, L is Th, L is Dy, L is Ho, L
is Er, L is Tm, L is Yb, and L is Lu.

[0051]In another embodiment of the catalyst compositions described by the
above empirical formulas, the catalyst composition contains no tantalum.

[0053]In one embodiment of the catalyst compositions described by the
above empirical formulas, the catalyst additionally contains lithium and
may optionally contain one or more other alkali metals. In this
embodiment the catalyst composition comprises a mixed oxide of the
empirical formula

Mo1VaSb.sub.bNbcTedXeLfAgLi.sub.hOn

wherein X, L, a, b, c, d, e, f, and n are previously described herein, A
is at least one of Na, K, Cs, Rb and mixtures thereof, 0≦g<0.1,
0≦h<0.1, and "g" and "h" represent the molar ratio of the
corresponding element to one mole of Mo. In other embodiments of the
catalyst composition comprising a mixed oxide described by the above
empirical formula, the catalyst composition contains no Na, K, Cs, Rb or
mixtures thereof (i.e. g equals 0). In other embodiments of the catalyst
composition comprising a mixed oxide described by the above empirical
formula, 0<h, 0.03<h, h<0.06, h<0.1.

[0054]The catalyst of the present invention may be made either supported
or unsupported (i.e. the catalyst may comprise a support or may be a bulk
catalyst). Suitable supports are silica, alumina, zirconia, titania, or
mixtures thereof. However, when zirconia or titania are used as support
materials then the ratio of molybdenum to zirconium or titanium increases
over the values shown in the above formulas, such that the Mo to Zr or Ti
ratio is between about 1:1 to 1:10. A support typically serves as a
binder for the catalyst resulting in a harder and more attrition
resistant catalyst. However, for commercial applications, an appropriate
blend of both the active phase (i.e. the complex of catalytic oxides
described above) and the support is helpful to obtain an acceptable
activity and hardness (attrition resistance) for the catalyst.
Directionally, any increase in the amount of the active phase decreases
the hardness of the catalyst. The support comprises between 10 and 90
weight percent of the supported catalyst. Typically, the support
comprises between 40 and 60 weight percent of the supported catalyst. In
one embodiment of this invention, the support may comprise as little as
about 10 weight percent of the supported catalyst. In one embodiment of
this invention, the support may comprise as little as about 30 weight
percent of the supported catalyst. In another embodiment of this
invention, the support may comprise as much as about 70 weight percent of
the supported catalyst. Support materials are available which may contain
one or more promoter elements, e.g. a silica sol containing sodium (Na),
and such promoter elements may be incorporated into the catalyst via the
support material. In one embodiment, the support comprises a low-sodium
silica.

Catalyst Preparation

[0055]The catalyst useful for the instant invention may be produced by a
variety of methods. Described herein are two possible synthesis methods.
The first synthesis method is carried out under approximately atmospheric
pressure (hereinafter referred to as the non-hydrothermal method or
synthesis) while the second synthesis method is done under elevated
pressures, typically in an autoclave, (hereinafter the hydrothermal
method or synthesis). Non-hydrothermal synthesis methods are described in
U.S. Pat. No. 6,514,902, U.S. Pat. No. 7,087,551, U.S. Pat. No. ,109,144,
WO 2004/108278 and WO 2006/019078, which are incorporated herein by
reference.

[0056]In one embodiment, the catalyst of the instant invention may be
prepared by the non-hydrothermal synthesis as follows: Ammonium
heptamolybdate, ammonium metavanadate and diantimony trioxide are added
to water, followed by heating of the resultant mixture to temperatures of
at least 50° C. and thereby obtain an aqueous mixture (A). In an
embodiment heating is performed while stirring the mixture.
Advantageously the aqueous mixture is heated to temperatures in the range
upward from 70° C. to the normal boiling point of the mixture. The
heating may be performed under reflux by using equipment having a reflux
condenser. In the case of heating under reflux, the boiling point
generally is in the range of from about 101° C. to 102° C.
Elevated temperatures are maintained for 0.5 hour or more. When the
heating temperature is low (e.g., lower than 50° C.), the heating
time needs to be long. When the heating temperature is in a range of from
80° C. to 100° C., the heating time is typically in a range
of from 1 to 5 hours.

[0057]Beneficially, after the heating, silica sol and hydrogen peroxide
are added to the aqueous mixture (A). When hydrogen peroxide is added to
the aqueous mixture (A), the amount of the hydrogen peroxide is such that
the molar ratio of hydrogen peroxide to antimony (H2O2/Sb molar
ratio) compound in terms of antimony is in the range of from 0.01 to 20,
in the range of from 0.5 to 3, in the range of from 1 to 2.5. After
addition of hydrogen peroxide, aqueous mixture (A) is stirred at
temperatures in the range of from 30° C. to 70° C. for from
30 minutes to 2 hours.

[0058]An aqueous liquid (B) is obtained by adding a niobium compound
(e.g., niobic acid) to water, followed by heating of the resultant
mixture to temperatures in a range of from 50° C. up to nearly
100° C. Advantageously aqueous liquid (B) contains a dicarboxylic
acid (e.g., oxalic acid) in addition to the niobium compound. Generally,
the molar ratio of the dicarboxylic acid to the niobium compound in terms
of niobium is in the range of from 1 to 4, advantageously in the range of
from 2 to 4. That is, in this case, niobic acid and oxalic acid are added
to water, followed by heating and stirring of the resultant mixture to
thereby obtain an aqueous liquid (B).

[0059]A useful method for preparing the above-mentioned aqueous liquid
(B), comprises the following steps: (1) mixing water, a dicarboxylic acid
(e.g. oxalic acid) and a niobium compound (e.g. niobic acid) thereby
obtaining a preliminary niobium-containing aqueous solution or a
niobium-containing aqueous mixture having suspended therein a part of the
niobium compound; (2) cooling the preliminary niobium-containing aqueous
solution or niobium-containing aqueous mixture thereby precipitating a
part of the dicarboxylic acid; and (3) removing the precipitated
dicarboxylic acid from the preliminary niobium-containing aqueous
solution, or removing the precipitated dicarboxylic acid and the
suspended niobium compound from the niobium-containing aqueous mixture,
thereby obtaining a niobium-containing aqueous liquid (B). Aqueous
liquids (B) obtained in the above method usually have a dicarboxylic
acid/niobium molar ratio within the range of from about 2 to 4.

[0060]A particularly useful dicarboxylic acid is oxalic acid, and useful
niobium compounds in step (1) of this method include niobic acid, niobium
hydrogen oxalate and ammonium niobium oxalate. These niobium compounds
can be used in the form of a solid, a mixture, or a dispersion in an
appropriate medium. When either niobium hydrogen oxalate or ammonium
niobium oxalate is used as the niobium compound, the dicarboxylic acid
may not be used. When niobic acid is used as the niobium compound, in
order to remove acidic impurities with which the niobic acid may have
been contaminated during the production thereof, the niobic acid may be
washed with an aqueous ammonia solution and/or water prior to use. In an
embodiment, freshly prepared niobium compound can be used as the niobium
compound. However, in the above-mentioned method, a niobium compound can
be used which is slightly denatured (for example by dehydration) as a
result of a long-term storage and the like. In step (1) of this method,
the dissolution of the niobium compound can be promoted by the addition
of a small amount of aqueous ammonia or by heating.

[0061]The concentration of the niobium compound (in terms of niobium) in
the preliminary niobium-containing aqueous solution or aqueous mixture
can be maintained within the range of from 0.2 to 0.8 mol/kg of the
solution or mixture. In an embodiment, dicarboxylic acid can be used in
an amount such that the molar ratio of dicarboxylic acid to niobium
compound in terms of niobium is approximately 3 to 6. When an excess
amount of the dicarboxylic acid is used, a large amount of the niobium
compound can be dissolved in the aqueous solution of dicarboxylic acid;
however, a disadvantage is likely to arise in that the amount of the
dicarboxylic acid which is caused to precipitate by cooling the obtained
preliminary niobium-containing aqueous solution or mixture becomes too
large, thus decreasing the utilization of the dicarboxylic acid. On the
other hand, when an unsatisfactory amount of the dicarboxylic acid is
used, a disadvantage is likely to arise in that a large amount of the
niobium compound remains undissolved and is suspended in the aqueous
solution of the dicarboxylic acid to form a mixture, wherein the
suspended niobium compound is removed from the aqueous mixture, thus
decreasing the degree of utilization of the niobium compound.

[0062]Any suitable method of cooling may be used in step (2). For example,
the cooling can be performed simply by means of an ice bath.

[0063]The removal of the precipitated dicarboxylic acid (or precipitated
dicarboxylic acid and the dispersed niobium compound) in step (3) can be
easily performed by conventional methods, for example, by decantation or
filtration.

[0064]When the dicarboxylic acid/niobium molar ratio of the obtained
niobium-containing aqueous solution is outside the range of from about 2
to 4, either the niobium compound or dicarboxylic acid may be added to
the aqueous liquid (B) so that the dicarboxylic acid/niobium molar ratio
of the solution falls within the above-mentioned range. However, in
general, such an operation is unnecessary since an aqueous liquid (B)
having the dicarboxylic acid/niobium molar ratio within the range of from
2 to 4 can be prepared by appropriately controlling the concentration of
the niobium compound, the ratio of the dicarboxylic acid to the niobium
compound and the cooling temperature of the above-mentioned preliminary
niobium-containing aqueous solution or aqueous mixture.

[0065]The aqueous liquid (B) may also be prepared comprising further
component(s). For example, at least a part of the aqueous liquid (B)
containing a niobium compound or containing a mixture of a niobium
compound and a dicarboxylic acid is used together with hydrogen peroxide.
In this case, it is beneficial that the amount of hydrogen peroxide
provided a molar ratio of hydrogen peroxide to niobium compound
(H2O2/Nb molar ratio) in terms of niobium is in the range of
from 0.5 to 20, from 1 to 20.

[0066]In another example, at least part of the aqueous liquid (B),
containing a niobium compound or containing a mixture of a niobium
compound and a dicarboxylic acid, or a mixture thereof with hydrogen
peroxide, further comprises an antimony compound (e.g. diantimony
trioxide), a titanium compound (e.g. titanium dioxide, which can be a
mixture of rutile and anatase forms) and/or a cerium compound (e.g.
cerium acetate). In this case, the amount of the hydrogen peroxide is
such that the molar ratio of hydrogen peroxide to niobium compound
(H2O2/Nb molar ratio) in terms of niobium is in the range of
from 0.5 to 20, from 1 to 20. In another example, the antimony compound
mixed with at least a part of the aqueous liquid (B) and the hydrogen
peroxide is such that the molar ratio (Sb/Nb molar ratio) of the antimony
compound in terms of antimony to the niobium compound in terms of niobium
is not more than 5, in the range of from 0.01 to 2.

[0067]Aqueous mixture (A) and aqueous liquid (B) are mixed together in an
appropriate ratio in accordance with the desired composition of the
catalyst, to thereby provide an aqueous mixture of ingredients,
typically, in the form of a slurry. The content of ingredients in the
aqueous mixture is generally in a range upward from about 50 percent by
weight, from 70 to 95 percent by weight, from 75 to 90 percent by weight.

[0068]In the case of producing a silica carrier-supported catalyst of the
present invention, the aqueous raw material mixture is prepared so as to
contain a source of silica (namely, a silica sol or fumed silica). The
amount of the source of silica can be appropriately adjusted in
accordance with the amount of the silica carrier in the catalyst to be
obtained.

Drying Step

[0069]The aqueous mixture of ingredients is dried to thereby provide a dry
catalyst precursor. Drying may be conducted by conventional methods, such
as spray drying or evaporation drying. Spray drying is particularly
useful, because a fine, spherical, dry catalyst precursor is obtained.
The spray drying can be conducted by centrifugation, by the two-phase
flow nozzle method or by the high-pressure nozzle method. As a heat
source for drying, it is an embodiment to use air which has been heated
by steam, an electric heater and the like. It is an embodiment that the
temperature of the spray dryer at an entrance to the dryer section
thereof is from 150° C. to 300° C.

Calcination Step

[0070]The dry catalyst precursor is converted into a mixed metal oxide
catalyst by calcination. Calcinations can be conducted using a rotary
kiln, a fluidized-bed kiln, fluidized bed reactor, fixed bed reactor, or
the like. Conditions of calcination are preselected such that the
catalyst formed has a specific surface area of from about 5 m2/g to
about 35 m2/g, from about 15 m2/g to about 20 m2/g.
Calcination involves heating the dry catalyst precursor up to a final
temperature in the range of about 600-680° C.

[0071]In the present invention, calcination process comprises heating of
the dry catalyst precursor continuously or intermittently to elevate from
a temperature which is less than 200° C. to a precalcination
temperature of not greater than about 400° C., not greater than
about 350° C., not greater than about 300° C. at a rate of
greater than 15° C./min. In an embodiment, the precalcination
temperature is 300° C. In an embodiment the heating rate is about
20° C./min. In another embodiment, the heating rate is 25°
C./min. In another embodiment, the heating rate is 30° C./min. Yet
in another embodiment, the dry catalyst precursor is introduced into a
hot calciner maintained at about 300° C. or slightly higher in
order to allow the temperature of the precursor to quickly increase to
about 300° C.

[0072]The heating rate from the precalcination temperature to the final
temperature can be about 0.5° C./min, 1° C./min, 2°
C./min or 5° C./min or any rate in the range of 0.5-5°
C./min. In one embodiment, the heating rate for the temperature range of
about 300° C. to the intermediate temperature is about 1°
C./min and from the intermediate temperature to the final temperature,
the heating rate is greater than 15° C./min, or greater than or
equal to 20° C./min, or greater than or equal to 25°
C./min, or greater than or equal to 30° C./min. In another
embodiment, the solid can be cooled after attaining the intermediate
temperature and then heated to the final temperature at a heating rate of
greater than about 15° C./min, or greater than or equal to
20° C./min, or greater than or equal to 25° C./min, or
greater than or equal to 30° C./min.

[0073]In one embodiment of the invention, the calcination is done in two
calcination stages: (1) up to intermediate or precalcination temperature
and (2) from intermediate or precalcination to final temperature. In one
embodiment the solid from the stage (1) calcination, optionally cooled,
is introduced into a hot calciner maintained at a temperature equal to
about the final temperature in order to allow the temperature of the
precursor to quickly increase to the final temperature.

[0074]In one embodiment, the heating rate for the temperature range of
about 300° C. to about 340-350° C., 345° C. is about
0.5° C./min or 1° C./min or about 2° C./min or about
5° C./min or any rate in the range of 0.5 to 5° C./min. In
one embodiment, the solid is held at a temperature in the range of
300-400° C., in the range of 340-350° C., at 345° C.
for a period of about 1 to 4 hours. In one embodiment, the solid is
heated at a rate of 2.45° C./min in the temperature range of
345-680° C.

[0075]Upon attaining the final temperature, the solid can be held at that
temperature for a period of from about 1 hour to about 3 hours, about 2
hours. The final temperature can be 600° C., 610° C.,
620° C., 630° C., 640° C., 650° C,
660° C., 670° C., and 680° C. or any temperature in
the 600-680° C. range. In one embodiment, the solid is heated at
rate a rate of 0.5° C./min from about 600° C. to about
680° C. In one embodiment, the solid is heated at rate a rate of
1° C./min from about 600° C. to about 680° C.

[0076]The calcination can be conducted in air or under a flow of air.
However, at least a part of the calcination is conducted in an atmosphere
of a gas (e.g., under a flow of a gas), such as nitrogen gas that is
substantially free of oxygen. The present invention contemplates using
inert gas. The inert gas can comprise a noble gas. The gas can comprise
nitrogen. The gas can comprise selection from air, steam, super heated
steam, carbon monoxide, and carbon dioxide. In one embodiment of the
present invention the calcination can be carried out under a flow of
nitrogen gas that is substantially free of oxygen for both the
temperature ranges of (1) up to about 400-450° C. and (2) above
about 400-450° C. In another embodiment of the present invention
the calcination can be carried out under a flow of air for the
temperature range of (1) up to about 400-450° C. and under a flow
of nitrogen gas that is substantially free of oxygen for the temperature
range of (2) above about 400-450° C. The flow rate of gas can be
critical especially for the temperature range of (1) up to about
400-450° C. The flow rate of gas can be in the range of about 0.67
to about 2.5 sccm per g catalyst precursor per minute.

[0077]In one embodiment a catalyst precursor is calcined under nitrogen in
a 1 foot vertical tube in two steps. After raising the temperature of the
loaded 1 foot vertical tube at the rate of about 1.2° C./min, to
345° C., the temperature is maintained at 345° C. for 4
hours. In the 2nd step the temperature was further raised at the
rate of about 2.3° C./min to a temperature of 640° C. After
dwelling for 2 hours at 640° C., the calcination is completed.

Incorporation of Tellurium

[0078]Tellurium may be incorporated into the catalyst by the addition of a
tellurium source compound to any one of aqueous mixture (A), aqueous
mixture (B), or a mixture of aqueous mixture (A) and aqueous mixture (B).
In one embodiment, tellurium may be added to the catalyst by
impregnation. In one embodiment, impregnation is carried out by
contacting calcined catalyst prepared by a method as described in this
application with a solution of Te(OH)6 and water. This solution is added
to the catalyst with stirring until the catalyst reached a point of
incipient wetness producing a catalyst with the desired level of
tellurium per mole of molybdenum on the catalyst surface. The catalyst is
then dried, typically by placing the catalyst in a 90° C. oven
overnight to dry in air. The dried impregnated material is then subjected
to a heat treatment, typically under nitrogen at 450° C. for 2
hours.

[0080]In general, the catalyst compositions described herein can be
prepared by hydrothermal synthesis where source compounds (i.e. compounds
that contain and/or provide one or more of the metals for the mixed metal
oxide catalyst composition) are admixed in an aqueous solution to form a
reaction medium and reacting the reaction medium at elevated pressure and
elevated temperature in a sealed reaction vessel for a time sufficient to
form the mixed metal oxide. In one embodiment, the hydrothermal synthesis
continues for a time sufficient to fully react any organic compounds
present in the reaction medium, for example, solvents used in the
preparation of the catalyst or any organic compounds added with any of
the source compounds supplying the mixed metal oxide components of the
catalyst composition. This embodiment simplifies further handling and
processing of the mixed metal oxide catalyst.

[0081]The source compounds are reacted in the sealed reaction vessel at a
temperature greater than 100° C. and at a pressure greater than
ambient pressure to form a mixed metal oxide precursor. In one
embodiment, the source compounds are reacted in the sealed reaction
vessel at a temperature of at least about 125° C., in another
embodiment at a temperature of at least about 150° C., and in yet
another embodiment at a temperature of at least about 175° C. In
one embodiment, the source compounds are reacted in the sealed reaction
vessel at a pressure of at least about 25 psig, and in another embodiment
at a pressure of at least about 50 psig, and in yet another embodiment at
a pressure of at least about 100 psig. Such sealed reaction vessels may
be equipped with a pressure control device to avoid over pressurizing the
vessel and/or to regulate the reaction pressure.

[0082]In one or more embodiments, the source compounds are reacted by a
protocol that comprises mixing the source compounds during the reaction
step. The particular mixing mechanism is not critical, and can include
mixing (e.g., stirring or agitating) the components during the reaction
by any effective method. Such methods include, for example, agitating the
contents of the reaction vessel by shaking, tumbling or oscillating the
component-containing reaction vessel. Such methods also include, for
example, stirring by using a stirring member located at least partially
within the reaction vessel and a driving force coupled to the stirring
member or to the reaction vessel to provide relative motion between the
stirring member and the reaction vessel. The stirring member can be a
shaft-driven and/or shaft-supported stirring member. The driving force
can be directly coupled to the stirring member or can be indirectly
coupled to the stirring member (e.g., via magnetic coupling). The mixing
is generally sufficient to mix the components to allow for efficient
reaction between components of the reaction medium to form a more
homogeneous reaction medium (e.g., and resulting in a more homogeneous
mixed metal oxide precursor) as compared to an unmixed reaction. This
results in more efficient consumption of starting materials and in a more
uniform mixed metal oxide product. Mixing the reaction medium during the
reaction step also causes the mixed metal oxide product to form in
solution rather than on the sides of the reaction vessel. This allows
more ready recovery and separation of the mixed metal oxide product by
techniques such as centrifugation, decantation, or filtration and avoids
the need to recover the majority of product from the sides of the reactor
vessel. More advantageously, having the mixed metal oxide form in
solution allows for particle growth on all faces of the particle rather
than the limited exposed faces when the growth occurs out from the
reactor wall.

[0083]It is generally desirable to maintain some headspace in the reactor
vessel. The amount of headspace may depend on the vessel design or the
type of agitation used if the reaction mixture is stirred. Overhead
stirred reaction vessels, for example, may take 50% headspace. Typically,
the headspace is filled with ambient air which provides some amount of
oxygen to the reaction. However, the headspace, as is known the art, may
be filled with other gases to provide reactants like O2 or even an
inert atmosphere such as Ar or N2. The amount of headspace and gas
within it depends upon the desired reaction as is known in the art.

[0084]The source compounds can be reacted in the sealed reaction vessel at
an initial pH of not more than about 4. Over the course of the
hydrothermal synthesis, the pH of the reaction mixture may change such
that the final pH of the reaction mixture may be higher or lower than the
initial pH. In one or more embodiments, the source compounds are reacted
in the sealed reaction vessel at a pH of not more than about 3.5. In some
embodiments, the components can be reacted in the sealed reaction vessel
at a pH of not more than about 3.0, of not more than about 2.5, of not
more than about 2.0, of not more than about 1.5 or of not more than about
1.0, of not more than about 0.5 or of not more than about 0. In one or
more embodiments, the pH ranges from about 0 to about 4, and in other
embodiments, from about 0.5 to about 3.5. In some embodiments, the pH can
range from about 0.7 to about 3.3, or from about 1 to about 3. The pH may
be adjusted by adding acid or base to the reaction mixture.

[0085]The source compounds can be reacted in the sealed reaction vessels
at the aforementioned reaction conditions (including for example,
reaction temperatures, reaction pressures, pH, stirring, etc., as
described above) for a period of time sufficient to form the mixed metal
oxide. In one or more embodiments, the mixed metal oxide comprises a
solid state solution comprising the required elements as discussed above,
and in certain embodiments at least a portion thereof includes the
requisite crystalline structure for active and selective propane or
isobutane oxidation and/or ammoxidation catalysts, as described below.
The exact period of time is not narrowly critical, and can include for
example at least about six hours, at least about twelve hours, at least
about eighteen hours, at least about twenty-four hours, at least about
thirty hours, at least about thirty-six hours, at least about forty-two
hours, at least about forty-eight hours, at least about fifty-four hours,
at least about sixty hours, at least about sixty-six hours or at least
about seventy-two hours. Reaction periods of time can be even more than
three days, including for example at least about four days, at least
about five days, at least about six days, at least about seven days, at
least about two weeks or at least about three weeks or at least about one
month.

[0086]Following the reaction step, further steps of the catalyst
preparation methods can include work-up steps, including for example
cooling the reaction medium comprising the mixed metal oxide (e.g., to
about ambient temperature), separating the solid particulates comprising
the mixed metal oxide from the liquid (e.g., by centrifuging and/or
decanting the supernatant, or alternatively, by filtering), washing the
separated solid particulates (e.g., using distilled water or deionized
water), repeating the separating step and washing steps one or more
times, and effecting a final separating step. In one embodiment, the work
up step comprises drying the reaction medium, such as by rotary
evaporation, spray drying, freeze drying etc. This eliminates the
formation of a metal containing waste stream.

[0087]After the work-up steps, the washed and separated mixed metal oxide
can be dried. Drying the mixed metal oxide can be effected under ambient
conditions (e.g., at a temperature of about 25° C. at atmospheric
pressure), and/or in an oven. In one or more embodiments, the mixed metal
oxide may be dried at a temperature ranging from about 40° C. to
about 150° C., and in one embodiment of about 120° C., over
a drying period of about time ranging from about five to about fifteen
hours, and in one embodiment of about twelve hours. Drying can be
effected under a controlled or uncontrolled atmosphere, and the drying
atmosphere can be an inert gas, an oxidative gas, a reducing gas or air.
In one or more embodiments, the drying atmosphere includes air.

[0088]As a further preparation step, the dried mixed metal oxide can be
treated to form the mixed metal oxide catalyst. Such treatments can
include for example calcinations (e.g., including heat treatments under
oxidizing or reducing conditions) effected under various treatment
atmospheres. The work-up mixed metal oxide can be crushed or ground prior
to such treatment, and/or intermittently during such pretreatment. In one
or more embodiments, the dried mixed metal oxide can be optionally
crushed, and then calcined to form the mixed metal oxide catalyst. The
calcination may be effected in an inert atmosphere such as nitrogen. In
one or more embodiments, calcination conditions include temperatures
ranging from about 400° C. to about 700° C., in certain
embodiments, from about 500° C. to about 650° C., and in
some embodiments, the calcination can be effected at about 600° C.

[0089]The treated (e.g., calcined) mixed metal oxide can be further
mechanically treated, including for example by grinding, sieving and
pressing the mixed metal oxide into its final form for use in fixed bed
or fluid bed reactors. As is known in the art, grinding may be
accomplished by using various methods, including jar milling, bead
beating, and the like. Optimal grinding conditions may be selected
depending upon the sample size and catalyst composition. In one
embodiment, an unsupported catalyst of about 2 grams may be ground in a
bead beater for from about 2 to about 15 minutes.

[0090]In one or more embodiments, the catalyst may be shaped into its
final form prior to any calcinations or other heat treatment. For
example, in the preparation of a fixed bed catalyst, the catalyst
precursor slurry is typically dried by heating at an elevated temperature
and then shaped (e.g. extruded, pelletized, etc.) to the desired fixed
bed catalyst size and configuration prior to calcination. Similarly, in
the preparation of fluid bed catalysts, the catalyst precursor slurry may
be spray dried to yield microspheroidal catalyst particles having
particle diameters in the range from 10 to 200 microns and then calcined.

[0091]For the catalyst preparation methods described herein, source
compounds containing and providing the metal components used in the
various synthesis methods of the catalyst (also referred to herein as a
"source" or "sources") can be provided to the reaction vessel as aqueous
solutions of the metal salts. Some source compounds of the metal
components can be provided to the reaction vessels as solids or as
slurries comprising solid particulates dispersed in an aqueous media.
Some source compounds of the metal components can be provided to the
reaction vessels as solids or as slurries comprising solid particulates
dispersed in non-aqueous solvents or other non-aqueous media.

[0096]Solvents that may be used to prepare mixed metal oxides according to
the invention include, but are not limited to, water, alcohols such as
methanol, ethanol, propanol, diols (e.g. ethylene glycol, propylene
glycol, etc.), organic acids such as acetic acid, as well as other polar
solvents known in the art. In one or more embodiments, the metal source
compounds are at least partially soluble in the solvent, at least at the
reaction temperature and pressure, and in certain embodiments, the metal
source compounds are slightly soluble in the solvent. In one or more
embodiments, water is the solvent. Any water suitable for use in chemical
synthesis may be used. The water may, but need not be, distilled and/or
deionized.

[0097]The amount of aqueous solvent in the reaction medium may vary due to
the solubilities of the source compounds that are combined to form the
particular mixed metal oxide. The amount of aqueous solvent should at
least be sufficient to yield a slurry (a mixture of solids and liquids
which is able to be stirred) of the reactants. It is typical in
hydrothermal synthesis of mixed metal oxides to leave an amount of
headspace in the reactor vessel.

[0098]Variations on the above methods will be recognized by those skilled
in the art. For example a method for preparing the catalyst described
herein having the following empirical formula:

Mo V0.1-0.3Sb0.1-0.3Nb0.03-0.15Te0.01-0.03Ti0.05--
0.25LeOn

in which L is La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu and
mixtures thereof, "e" is greater than zero and less than about 0.02, and
"n" is determined by the oxidized states of the other elements, comprises
preparing solutions or slurries of source compounds for the catalyst. In
one or the first slurry, molybdenum trioxide (MoO3), antimony oxide
(Sb2O3), telluric acid (Te(OH)6), titanium dioxide
(TiO2), and at least one "L" source compound are dissolved/slurried
in water at the desired ratios (all ratios are relative to molybdenum
metal). In another or second solution or slurry, vanadium oxysulfate
(VOSO4) is dissolved/slurried in water. In an alternate embodiment,
vanadium oxysulfate may be added as a solid. In another or third solution
or slurry, niobic acid (Nb2O5.nH2O) is mixed with oxalic
acid (HO2CCO2H). A range of oxalic acid:niobium molar ratios
may be employed. In one embodiment the oxalic acid:niobium molar ratio is
about 3:1. The three solutions/slurries are combined with one another,
heated with mixing to 175° C. and held at this temperature for 67
hours, and then cooled to room temperature, typically by natural heat
dissipation. The cooled slurry is filtered to remove the mother liquor,
and the remaining solids are washed and then dried and then calcined
under nitrogen at 600° C. to activate the catalyst. The calcined
catalyst is pulverized, then pelletized and sized, or spray dried for
testing and/or ultimate use.

Conversion of Propane and Isobutane via Ammoxidation and Oxidation
Reactions

[0099]In one or more embodiments, propane is converted to acrylonitrile
and/or isobutane to methacrylonitrile, by providing one or more of the
aforementioned catalysts in a gas-phase flow reactor, and contacting the
catalyst with propane or isobutane in the presence of oxygen (e.g.
provided to the reaction zone in a feed stream comprising an
oxygen-containing gas, such as and typically air) and ammonia under
reaction conditions effective to form acrylonitrile or methacrylonitrile.
In certain embodiments, the feed stream comprises propane or isobutane,
an oxygen-containing gas such as air, and ammonia, with the following
molar ratios. In one or more embodiments, the molar ratio of propane or
isobutane to oxygen is from about 0.125 to about 5, in other embodiments
from about 0.25 to about 4, and in yet other embodiments, from about 0.5
to about 3.5. In one or more embodiments, the molar ratio of propane or
isobutane to ammonia is from about 0.3 to about 2.5, and in other
embodiments, from about 0.5 to about 2.0. The feed stream can also
comprise one or more additional feed components, including acrylonitrile
or methacrylonitrile product (e.g., from a recycle stream or from an
earlier-stage of a multi-stage reactor), and/or steam. For example, the
feed stream can comprise about 5% to about 30% by weight of one or more
additional feed components, relative to the total amount of the feed
stream, or by mole relative to the amount of propane or isobutane in the
feed stream. In one embodiment the catalyst compositions described herein
are employed in the ammoxidation of propane to acrylonitrile in a
once-through process, i.e., without recycle of recovered but unreacted
feed materials.

[0100]Propane can also be converted to acrylic acid and isobutane to
methacrylic acid by providing one or more of the aforementioned catalysts
in a gas-phase flow reactor, and contacting the catalyst with propane in
the presence of oxygen (e.g. provided to the reaction zone in a
feedstream comprising an oxygen-containing gas, such as and typically
air) under reaction conditions effective to form acrylic acid. The feed
stream for this reaction preferably comprises propane and an
oxygen-containing gas such as air in a molar ratio of propane or
isobutane to oxygen ranging from about 0.15 to about 5, and preferably
from about 0.25 to about 2. The feed stream can also comprise one or more
additional feed components, including acrylic acid or methacrylic acid
product (e.g., from a recycle stream or from an earlier-stage of a
multi-stage reactor), and/or steam. For example, the feed steam can
comprise about 5% to about 30% by weight relative to the total amount of
the feed stream, or by mole relative to the amount of propane or
isobutane in the feed stream.

[0101]The specific design of the gas-phase flow reactor is not narrowly
critical. Hence, the gas-phase flow reactor can be a fixed-bed reactor, a
fluidized-bed reactor, or another type of reactor. The reactor can be a
single reactor, or can be one reactor in a multi-stage reactor system. In
one or more embodiments, the reactor comprises one or more feed inlets
for feeding a reactant feed stream to a reaction zone of the reactor, a
reaction zone comprising the mixed metal oxide catalyst, and an outlet
for discharging reaction products and unreacted reactants.

[0102]The reaction conditions are controlled to be effective for
converting the propane to acrylonitrile or acrylic acid, or for
converting the isobutane to methacrylonitrile or methacrylic acid.
Generally, reaction conditions include a temperature ranging from about
300° C. to about 550° C., in one or more embodiments from
about 325° C. to about 500° C., in some embodiments from
about 350° C. to about 450° C., and in other embodiments
from about 430° C. to about 520° C. The pressure of the
reaction zone can be controlled to range from about 0 psig to about 200
psig, in one or more embodiments from about 0 psig to about 100 psig, and
in some embodiments from about 0 psig to about 50 psig.

[0103]Generally, the flow rate of the propane or isobutane containing feed
stream through the reaction zone of the gas-phase flow reactor can be
controlled to provide a weight hourly space velocity (WHSV) ranging from
about 0.02 to about 5, in some embodiments from about 0.05 to about 1,
and in other embodiments from about 0.1 to about 0.5, in each case, for
example, in grams of propane or isobutane to grams of catalyst. In one or
more embodiments, advantageous catalyst performance is seen when the WHSV
is at least about 0.1, in other embodiments at least about 0.15, and in
yet other embodiments, at least about 0.2.

[0104]The resulting acrylonitrile and/or acrylic acid and/or
methacrylonitrile and/or methacrylic acid product can be isolated, if
desired, from other side-products and/or from unreacted reactants
according to methods known in the art.

[0105]One or more embodiments of the present invention, when employed in
the single pass (i.e. no recycle) ammoxidation of propane, are capable of
producing a yield of at least about 57 percent acrylonitrile. Certain
embodiments of the present invention, when employed in the single pass
(i.e. no recycle) ammoxidation of propane, are capable of producing a
yield of at least about 59 percent acrylonitrile. Other embodiments of
the present invention, when employed in the single pass (i.e. no recycle)
ammoxidation of propane, are capable of producing a yield of at least
about 61 percent acrylonitrile. The effluent of the reactor may also
include COX (carbon dioxide+carbon monoxide), hydrogen cyanide (HCN),
acetonitrile or methyl cyanide (CH3CN), unreacted oxygen (O2),
ammonia (NH3), nitrogen (N2), helium (He), and entrained
catalyst fines.

[0106]Advantageously, the catalyst compositions of the present invention
differ from tellurium-containing catalysts described in the literature in
that the catalyst compositions of the present invention do not exhibit
any observable tellurium loss from the active phase when prepared and
tested under the conditions described hereinabove. For example, in one or
more embodiments, no observable tellurium deposit is formed in the
calcination vessel or the calcination furnace when the catalyst
compositions of the present invention are calcined for about 2 hours
under nitrogen at a temperature of about 600° C. The catalyst
compositions of the present invention exhibit enhanced stability when
compared to other tellurium-containing catalysts. This enhanced stability
results in less degradation in catalyst performance with time on-stream,
and also enables the catalyst to maintain good performance at higher
space velocity.

Specific Embodiments

[0107]In order to illustrate the instant invention, mixed metal oxide
catalyst were prepared and then evaluated under various reaction
conditions. The compositions listed below are nominal compositions, based
on the total metals added in the catalyst preparation. Since some metals
may be lost or may not completely react during the catalyst preparation,
the actual composition of the finished catalyst may vary slightly from
the nominal compositions shown below.

EXAMPLE #1

Mo1V03Sb0.175Nb0.06Te0.02Ti0.1Nd0.005O.-
sub.n

[0108]A 125 mL Teflon reactor liner was loaded with MoO3 (8.0 g),
Sb2O3 (1.418 g), TiO2 (0.444 g), Te(OH)6 (0.255 g),
and Nd(OAc)3 (2.78 mL of a 0.1 M solution) and water (10 mL). As
used in this example and several subsequent examples, "(OAc)3"
designates the acetate hydrate for the named lanthanide metal. The
mixture was stirred for about 5 minutes, after which time was introduced
VOSO4 (16.67 mL of a 1 M solution) and niobium oxalate (7.39 mL of a
0.451 M solution where the molar ratio of oxalate to niobium is about
3/1). Water was added to obtain an about 80% fill volume in the reactor
liner. The reactor was then sealed with a Teflon cap in a metal housing,
placed in an oven preheated to 175° C. and continuously rotated to
effect mixing of the liquid and solid reagents. After 67 h (h=hours), the
reactor was cooled and the Teflon liner was removed from the housing. The
product slurry was stirred for 2 minutes, and then vacuum-filtered using
a glass frit and washed by the addition of 200 mL water in three
portions. The wet solid was then dried in air at 120° C. for 12 h.
The resulting solid material was crushed and calcined under N2 for 2
h at 600° C. The solid was then ground, pressed, and sieved to a
particle size range of 145 to 355 microns and tested for catalytic
performance. This material has the nominal composition
Mo1V0.3Sb0.175Nb0.06Te0.02Ti0.1Nd0.005-
On.

[0109]The material was tested as a catalyst for the heterogeneous
ammoxidation of propane to acrylonitrile. At 420° C., WHSV =0.2
and a feed ratio of C3H8/NH3/O2/He=1/1.2/3/12, an
acrylonitrile yield of 61% was obtained (89% propane conversion, 68%
acrylonitrile selectivity).

EXAMPLE #2

Mo1V0.3Sb0.18Nb0.08Te0.02Ti0.1Li0.016Nd-
0.005On

[0110]A first material was prepared as follows. A 23 mL Teflon reactor
liner was loaded with MoO3 (1.152 g), VOSO4 (2.30 mL of a 1.04
M solution), niobium oxalate (1.60 mL of a 0.40 M solution where the
molar ratio of oxalate to niobium is about 3/1), Sb2O3 (2.93 mL
of a 0.49 M slurry), TiO2 (2.85 mL of a 0.28 M slurry), Li(OAc)
(1.00 mL of a 0.40 M solution), Te(OH)6 (0.80 mL of a 0.20 M
solution), and Nd(OAc)3 (1.00 mL of a 0.04 M solution). Water was
added to obtain an about 60% fill volume in the reactor liner. The
reactor was then sealed with a Teflon cap in a metal housing, placed in
an oven preheated to 175° C. and continuously rotated to effect
mixing of the liquid and solid reagents. After 48 h the reactor was
cooled and the Teflon liner was removed from the housing. The product
slurry was stirred for 2 minutes, and then vacuum-filtered using a glass
frit and washed three times by the addition of 150 mL water in three
portions. The wet solid was then dried in air at 90° C. for 12 h.
The resulting solid material was crushed and calcined under N2 for 2
h at 600° C. This material has the nominal composition
Mo1V0.3Sb0.18Nb0.08Te0.02Ti0.1Li0.05Nd-
0.005On.

[0111]A second material was prepared as described above for the first
material, except that the lithium acetate was omitted. This second
material has the nominal composition
Mo1V0.3Sb0.18Nb0.08Te0.02Ti0.1Nd0.005O-
n.

[0112]A 0.45 g portion of the first material and a 0.94 g portion of the
second material were combined to form a sample having the nominal
composition
Mo1V0.3Sb0.18Nb0.08Te0.02Ti0.1Li0.016N-
d0.005On. The solid was then ground, pressed, and sieved to a
particle size range of 145 to 355 microns and tested for catalytic
performance.

[0113]The material was tested as a catalyst for the heterogeneous
ammoxidation of propane to acrylonitrile. At 433° C., WHSV=0.2 and
a feed ratio of C3H8/NH3/O2/N2=1/2.0/3/12, an
acrylonitrile yield of 60% was obtained (91% propane conversion, 65%
acrylonitrile selectivity).

COMPARATIVE EXAMPLE #3

Mo1V0.3Sb0.2Nb0.0.6Ti0.1Nd0.005On

[0114]A 125 mL Teflon reactor liner was loaded with MoO3 (8.0 g),
Sb2O3 (1.620 g), TiO2 (0.444 g), and Nd(OAc)3 (0.0893
g) and water (10 mL). The mixture was stirred for about 5 minutes, after
which time was introduced VOSO4 (16.67 mL of a 1 M solution) and
niobium oxalate (7.612 mL of a 0.438 M solution where the molar ratio of
oxalate to niobium is about 3/1). Water was added to obtain an about 80%
fill volume in the reactor liner. The reactor was then sealed with a
Teflon cap in a metal housing, placed in an oven preheated to 175°
C. and continuously rotated to effect mixing of the liquid and solid
reagents. After 48 h, the reactor was cooled and the Teflon liner was
removed from the housing. The product slurry was stirred for 2 minutes,
and then vacuum-filtered using a glass frit and washed by the addition of
200 mL water in three portions. The wet solid was then dried in air at
120° C. for 12 h. The resulting solid material was crushed and
calcined under N2 for 2 h at 600° C. The solid was then
ground, pressed, and sieved to a particle size range of 145 to 355
microns and tested for catalytic performance. This material has the
nominal composition
Mo1V0.3Sb0.2Nb0.06Ti0.1Nd0.005On.

[0115]The material was tested as a catalyst for the heterogeneous
ammoxidation of propane to acrylonitrile. At 430° C., WHSV=0.15
and a feed ratio of C3H8/NH3/O2/He=1/1.2/3/12, an
acrylonitrile yield of 56% was obtained (87% propane conversion, 64%
acrylonitrile selectivity).

COMPARATIVE EXAMPLE #4

Mo1V0.38Sb0.25Nb0.075Ti0.125Nd0.0062On

[0116]A 200 mL Teflon reactor liner was loaded with MoO3 (6.334 g),
Sb2O3 (1.283 g), TiO2 (0.351 g), Nd(OAc)3 (0.088 g)
and water (10 mL). The mixture was stirred for about 5 minutes, after
which time was introduced VOSO4 (13.2 mL of a 1.0 M solution) and
niobium oxalate (6.083 mL of a 0.434 M solution). Water was added to
obtain an about 80% fill volume of the reactor liner. The reactor was
then sealed with a Teflon cap in a metal housing, placed in an oven
preheated to 175° C. and continuously rotated to effect mixing of
the liquid and solid reagents. After 48 h the reactor was cooled and the
Teflon liner was removed from the housing. The product slurry was
centrifuged to separate the solid reaction products from the liquid. The
liquid was decanted and distilled water (25 mL) was added to the solid.
The solid was crushed and agitated to dissolve soluble salts. The mixture
was centrifuged and the liquid decanted. This washing was done twice. The
wet solid was dried in air at 120° C. for 12 h. The resulting
solid material was crushed and calcined under N2 for 2 h at
600° C. The solid was then ground, pressed, and sieved to a
particle size range of 145 to 355 microns and tested for catalytic
performance. This material has the nominal composition
Mo1V0.38Sb0.25Nb0.075Ti0.125Nd0.0062On-
.

[0117]The material was tested as a catalyst for the heterogeneous
ammoxidation of propane to acrylonitrile. At 420° C., WHSV=0.15,
and feed ratio C3H8/NH3/O2/He=1/1.2/3/12, an acrylonitrile
yield of 58% was achieved at a propane conversion of 84% and an
acrylonitrile selectivity of 69%.

COMPARATIVE EXAMPLE #5

Mo1V0.3Sb0.2Nb0.06Ti0.1Ge0.05Nd0.005O.s-
ub.n

[0118]A 23 mL Teflon reactor liner was loaded with MoO3 (1.20 g),
Sb2O3 (0.243 g), GeO2 (0.0436 g) and water (2.0 mL). The
mixture was stirred for about 5 minutes, after which time was introduced
VOSO4 (2.50 mL of a 1.0 M solution), TiO2 (0.833 mL of a 0.08
g/mL slurry), Nd(OAc)3 (0.417 mL of a 0.1 M solution), and niobium
oxalate (1.142 mL of a 0.438M solution). Water was added to obtain an
about 80% fill volume of the reactor liner. The reactor was then sealed
with a Teflon cap in a metal housing, placed in an oven preheated to
175° C. and continuously rotated to effect mixing of the liquid
and solid reagents. After 48 h the reactor was cooled and the Teflon
liner was removed from the housing. The product slurry was centrifuged to
separate the solid reaction products from the liquid. The liquid was
decanted and distilled water (5 mL) was added to the solid. The solid was
crushed and agitated to dissolve soluble salts. The mixture was
centrifuged and the liquid decanted. This washing was done twice. The wet
solid was dried in air at 120° C. for 12 h. The resulting solid
material was then crushed and calcined under N2 for 2 h at
600° C. The solid was then ground, pressed, and sieved to a
particle size range of 145 to 355 microns and tested for catalytic
performance. This material has the nominal composition
Mo1V0.3Sb0.2Nb0.06Ti0.1Ge0.05Nd0.005O.-
sub.n.

[0119]The material was tested as a catalyst for the heterogeneous
ammoxidation of propane to acrylonitrile. At 420° C., WHSV=0.15,
and feed ratio C3H8/NH3/O2/He=1/1.2/3/12 an
acrylonitrile yield of 58% was achieved at a propane conversion of 84%
and an acrylonitrile selectivity of 69%.

COMPARATIVE EXAMPLE #6 AND EXAMPLE #7

[0120]For Comparative Example 6, a base catalyst of formula
MoV0.21Sb0.24Nb0.09Ox/45% SiO2 (referred to
hereinafter as the "4 Component Base") was prepared by a non-hydrothermal
method and calcination method described herein. Similarly, for Example
#7, a catalyst of formula
MoV0.21Sb0.24Te0.04Nb0.09Ox/45% SiO2 was
prepared by additionally adding tellurium to the "4 Component Base"
catalyst using the impregnation method described herein.

COMPARATIVE EXAMPLES #8 AND #9 AND EXAMPLES #10 THROUGH #12

[0121]For Comparative Example #8, a base catalyst of formula
MoV0.3Sb0.2Nb0.08Ti0.1Ce0.005Ox/45%
SiO2 (referred to hereinafter as the "6 Component Base") was
prepared by a non-hydrothermal method and calcination method described
herein. Similarly for Comparative Example #9 and Examples #10 through
#12, the catalyst compositions shown below with varying tellurium content
were prepared by additionally adding tellurium to the "6 Component Base"
catalyst using the impregnation method described herein.

[0126]Catalysts of Comparative Examples #6 and #8 and Examples 7 and #9
through #12 were tested in a 40 cc lab fluid bed reactor having a
diameter of 1-inch. The reactor was charged with about 20 to about 45 g
of particulate catalyst or catalyst mixture. Propane was fed into the
reactor at a rate of about 0.04 to about 0.15 WHSV. Pressure inside the
reactor was maintained at about 2 to about 15 psig. Reaction temperatures
were in the range of about 420 to about 460° C. Generally, ammonia
was fed into the reactor at a flow rate such that ammonia to propane
ratio was from about 1 to about 1.5. Oxygen was fed into the reactor at a
flow rate such that oxygen to propane ratio was about 3.4. Nitrogen was
fed into the reactor at a flow rate such that nitrogen to propane ratio
was about 12.6. The testing results for the catalysts of Comparative
Examples #6 and #8 and Examples 7 and #9 through #12 are summarized in
Table 1 below.

[0127]For Comparative Example #13, a base catalyst of formula
MoV0.25Sb0.167Nb0.08Nd0.002Ce0.003Li0.013O.-
sub.x/45% SiO2 was prepared by a non-hydrothermal method and
calcination method described herein. Similarly for Examples #14 through
#15, the catalyst compositions shown below with varying tellurium content
were prepared by additionally adding tellurium to the catalyst using the
impregnation method described herein.

For the catalysts of Comparative Example #13 and Examples #14 and #15,
additional antimony (0.08 moles Sb/mole Mo) was added to the catalysts by
dusting the catalyst with Sb2O3. The catalysts were then tested
in a 40 cc lab fluid bed reactor under the same conditions described
above for the Comparative Example #6 and #8 and Examples #7 and #9
through #12. The testing results for the catalysts of Comparative Example
#13 and Examples #14 and #15 are summarized in Table 2 below:

[0130]As used in this application and in Tables 1 and 2 above, "Temp" is
the reactor temperature in degrees centigrade. "TIS" is the "time on
stream" in hours (h). "C3 conv" means propane conversion and is the
mole percent per pass conversion of propane to all products and
by-products. "AN sel" means acrylonitrile selectivity and is the ratio of
moles of acrylonitrile produced to moles of propane converted expressed
in percent. "AN yield" means acrylonitrile yield and is the mole percent
per pass conversion of propane to acrylonitrile. "WHSV" means the weight
hourly space velocity of the propane fed to the reactor and is expressed
as the weight of propane/weight of catalyst/hour, also known as "wwh".

[0131]While the foregoing description and the above embodiments are
typical for the practice of the instant invention, it is evident that
many alternatives, modifications, and variations will be apparent to
those skilled in the art in light of this description. Accordingly, it is
intended that all such alternatives, modifications and variations are
embraced by and fall within the spirit and broad scope of the appended
claims.